LTE vs 5G NR — Side-by-Side
A layer-by-layer comparison of LTE and 5G NR — architecture, PHY, protocol stack, mobility, security and voice, in one place.
5G NR did not throw LTE away — it kept the shape (OFDM air interface, a layered protocol stack, an IP core) and changed the details that mattered for speed, latency and flexibility. This page puts the two side by side, layer by layer, so you can map what you know in one onto the other. Each row links to the deeper page on both sides.
Architecture & Core
The biggest structural change is the core: LTE's EPC is a set of fixed nodes with point-to-point interfaces; 5G's 5GC is a Service-Based Architecture of network functions talking over a common bus, with control and user plane fully split.
| Aspect | LTE (EPS) | 5G (5GS) |
|---|---|---|
| Radio node | eNB (monolithic) | gNB, optionally split CU/DU/RU |
| Core | EPC — MME, S-GW, P-GW, HSS, PCRF | 5GC — AMF, SMF, UPF, UDM, AUSF, PCF, NRF, NSSF |
| Core style | Point-to-point interfaces (S1, S5, S6a…) | Service-Based Architecture (SBA), HTTP/2 APIs + reference points |
| CP/UP split | Partial (S-GW/P-GW carry both) | Full — SMF (control) vs UPF (user), CUPS by design |
| Control-plane anchor | MME | AMF (mobility) + SMF (session) |
| User-plane gateway | S-GW + P-GW | UPF (can be chained/distributed for edge) |
Deeper: EPS Architecture vs 5G System Architecture.
Air Interface & PHY
LTE fixed one numerology (15 kHz) and used SC-FDMA uplink; NR made numerology a choice, unified on CP-OFDM (with DFT-s-OFDM optional uplink), and replaced turbo with LDPC/Polar.
| Aspect | LTE | 5G NR |
|---|---|---|
| Subcarrier spacing | Fixed 15 kHz | 15·2μ kHz → 15/30/60/120/240 |
| Waveform | OFDMA DL, SC-FDMA UL | CP-OFDM DL & UL, DFT-s-OFDM optional UL |
| Slot | 0.5 ms (7 symbols, normal CP) | 14 symbols; length = 1/2μ ms |
| Resource block | 12 subcarriers × 7 symbols (defined in time+freq) | 12 subcarriers (frequency only) |
| Always-on RS | CRS across the whole band | None — DMRS/CSI-RS are on demand (lean carrier) |
| Channel coding | Turbo (data), TBCC (control) | LDPC (data), Polar (control) |
| Max modulation | 256QAM (Rel-12) | 256QAM (1024QAM later) |
| Bandwidth | ≤ 20 MHz per carrier (CA for more) | ≤ 100 MHz (FR1) / 400 MHz (FR2) per carrier |
| Bandwidth adaptation | Whole carrier | Bandwidth Parts (BWP) |
Deeper: LTE Frame Structure vs NR Frame & Numerology; LTE Reference Signals vs NR Reference Signals.
Control Channel & Scheduling
| Aspect | LTE | 5G NR |
|---|---|---|
| DL control | PDCCH in a control region (1–3 symbols) spanning the band; PCFICH/PHICH | PDCCH in a CORESET + search space (flexible in time/freq); no PHICH |
| UL HARQ | Synchronous, fixed timing (n+4 FDD) | Asynchronous, flexible timing (K1/K2, no PHICH) |
| Time-domain alloc | Fixed timing relations | SLIV (start symbol + length), mapping type A/B |
| Freq-domain alloc | RA type 0/1/2 (RBG bitmap / RIV) | RA type 0/1 (RBG bitmap / RIV) within a BWP |
| Grant-free UL | SPS | Configured Grant Type 1 & Type 2 |
Deeper: LTE PDCCH & DCI vs NR PDCCH & DCI; LTE HARQ vs NR HARQ.
Protocol Stack (MAC / RLC / PDCP / SDAP)
| Layer | LTE | 5G NR |
|---|---|---|
| New layer | — | SDAP (QoS-flow → DRB mapping) added on top of PDCP |
| RLC | Segmentation and concatenation; in-order at RLC | Segmentation only (no concatenation); ordering moved to PDCP |
| PDCP | Ciphering; integrity on SRB only; ROHC | Adds UP integrity, duplication, and out-of-order delivery option |
| MAC | 8 HARQ processes; sync UL HARQ | Up to 16 HARQ processes; async; BWP/SCell activation CEs |
| QoS granularity | Bearer-level (EPS bearer) | Flow-level (QoS flow, QFI) mapped to DRBs |
Deeper: LTE RLC (concatenation) vs NR RLC; SDAP (NR-only).
States & Mobility
| Aspect | LTE | 5G NR |
|---|---|---|
| RRC states | IDLE, CONNECTED (2) | IDLE, INACTIVE, CONNECTED (3) |
| Light-connection | Rel-13 suspend/resume (add-on) | RRC_INACTIVE native (RNA, I-RNTI, RAN paging) |
| Handover types | X2, S1 | Xn, N2 (NG), plus Conditional HO & DAPS |
| Measurement events | A1–A5, B1/B2 | A1–A6, B1/B2 (+ conditional events) |
| Reselection | S/R-criteria, priorities | Same framework, SSB-based |
Deeper: LTE RRC States vs NR RRC States; LTE X2 HO vs NR Xn HO.
QoS & Security
| Aspect | LTE | 5G NR |
|---|---|---|
| QoS unit | EPS bearer; QCI + ARP | QoS flow; 5QI + ARP, mapped to DRB by SDAP |
| Identifiers | QCI (scalar) | 5QI (superset, adds delay-critical GBR) |
| Permanent ID privacy | IMSI sent in clear at attach | SUPI concealed as SUCI (never sent in clear) |
| Key anchor | KASME → KeNB | KAUSF/KSEAF → KAMF → KgNB |
| User-plane integrity | Not supported | Supported (per-DRB) |
| Algorithms | EEA/EIA | NEA/NIA (same primitives: NULL, SNOW3G, AES, ZUC) |
Voice
| Aspect | LTE | 5G NR |
|---|---|---|
| Native voice | VoLTE over IMS (media on QCI=1, signalling on QCI=5) | VoNR over IMS (media on 5QI=1, signalling on 5QI=5) |
| Fallback | CSFB to 2G/3G if no VoLTE | EPS Fallback to LTE/VoLTE if no VoNR |
| Mid-call continuity | SRVCC (VoLTE → CS on coverage loss) | SRVCC (NR → LTE/UTRAN) where deployed |
| Circuit-switched fallback | Yes (CSFB) | No CS domain in 5GC — EPS Fallback is the analog |
Deeper: LTE Voice Options vs 5G Voice Options.
Interfaces at a Glance
| Purpose | LTE | 5G |
|---|---|---|
| RAN ↔ core (CP) | S1-MME (S1AP) | N2 (NGAP) |
| RAN ↔ core (UP) | S1-U (GTP-U) | N3 (GTP-U) |
| Inter-RAN | X2 (X2AP) | Xn (XnAP) |
| Intra-RAN split | — (monolithic eNB) | F1 (F1AP), E1 (E1AP) |
| Core session mgmt | S11/S5 (GTP-C) | N4 (PFCP), N7/N8/N10/N11 (SBI) |
| Subscriber DB | S6a (Diameter) | N8/N13 (SBI to UDM/AUSF) |
Use this with
This hub is a map; follow the per-row links into the full pages, and use the roadmap to pick a reading order.